Nowadays, USB technologies have been widely used in embedded electronic apparatuses. Specifically, a USB host is usually integrated in an embedded electronic apparatus to control USB devices (e.g., USB drives, USB mice and so on) plugged into the embedded electronic apparatuses to accomplish functions supported by the USB devices. Usually, the number of local endpoints in the USB host has already been defined during designing the chip of the USB host. It can be understood by those skilled in the art that, according to the protocol specified in the USB standard, the USB host obtains a function interface description information of a USB device according to an interface descriptor when the USB device is plugged in, then obtains remote endpoints corresponding to the function interface and establishes logic channels between the local endpoints and the remote endpoints. The local endpoints correspond to the remote endpoints and the logic channels are formed therebetween. Data transmission between the USB host and the USB device can be carried out via the logic channels to therefore achieve the functions supported by the USB device. In this case, the USB host is expected to support USB devices as much as possible. Under the circumstances that the number of local endpoints included in the USB host is smaller than the number of remote endpoints included in all USB logic devices expected to be supported by the host, some of the USB logic devices are impossible to establish channels with the USB host, since there is not enough local endpoints for pairing. Consequently, the functions of these USB logic devices would not be accomplished.
To solve the previously mentioned problems, a practice in the prior art is to redesign chip of the USB host to increase number of the local endpoints supported by the USB host or to increase the number of USB controllers. However, it costs and takes time to redesign the chip, which is unfavorable in production of the embedded electronic apparatuses.
Another practice in the prior art is to re-plan the USB functions of the embedded electronic apparatuses to reduce the number of USB logical devices and the corresponding functions supported by the USB host to comply with number of the local endpoints. However, it will impair market competitiveness of the embedded electronic apparatuses, which is unfavorable for marketing.
Thus, there remains a considerable need for devices and methods that can flexibly pair the USB host and the USB device even when the number of remote endpoints included in multiple USB logic devices is greater than the number of local endpoints included in the USB host.